Basic general education

Line UMK A. V. Peryshkin. Physics (7-9)

Introduction: state of aggregation of matter

State of aggregation - a state of a substance that has certain properties: the ability to maintain shape and volume, to have a long-range or short-range order, and others. When it changes aggregate state of matter there is a change physical properties, as well as density, entropy and free energy.

How and why do these amazing transformations take place? To understand this, remember that everything around is made up of. Atoms and molecules of various substances interact with each other, and it is the connection between them that determines what is the state of matter of matter.

There are four types of aggregates:

gaseous,

It seems that chemistry reveals its secrets to us in these amazing transformations. However, it is not. The transition from one state of aggregation to another, as well as or diffusion, are related to physical phenomena, since in these transformations no changes in the molecules of the substance occur and their chemical composition is preserved.

gaseous state

At the molecular level, a gas is a randomly moving, colliding with the walls of the vessel and with each other, molecules that practically do not interact with each other. Since the gas molecules are not interconnected, the gas fills the entire volume provided to it, interacting and changing direction only when they hit each other.

Unfortunately, it is impossible to see gas molecules with the naked eye and even with a light microscope. However, the gas can be touched. Of course, if you just try to catch gas molecules flying around in the palm of your hand, then you will not succeed. But surely everyone saw (or did it themselves) how someone inflated the tire of a car or bicycle with air, and from soft and wrinkled it became inflated and elastic. And the apparent "weightlessness" of gases will be refuted by the experiment described on page 39 of the textbook "Chemistry Grade 7" edited by O.S. Gabrielyan.

This is because a large number of molecules enter the closed limited volume of the tire, which become crowded, and they begin to hit each other and the tire walls more often, and as a result, the total effect of millions of molecules on the walls is perceived by us as pressure.

But if the gas occupies the entire volume provided to it, why then does it not fly off into space and spread throughout the universe, filling interstellar space? So, something still retains and limits the gases by the atmosphere of the planet?

Quite right. And this - gravitational force. In order to break away from the planet and fly away, the molecules need to develop a speed that exceeds the "escape speed" or second space velocity, and the vast majority of molecules move much more slowly.

Then the following question arises: why do gas molecules do not fall to the ground, but continue to fly? It turns out thanks to solar energy Air molecules have a solid supply of kinetic energy, which allows them to move against the forces of gravity.

The collection contains questions and tasks of various directions: settlement, qualitative and graphic; technical, practical and historical character. Tasks are divided into topics in accordance with the structure of the textbook “Physics. Grade 9" by authors A. V. Peryshkin, E. M. Gutnik and allow you to implement the requirements stated by the Federal State Educational Standards for meta-subject, subject and personal learning outcomes.

liquid state

By increasing the pressure and/or decreasing the temperature, gases can be converted into a liquid state. Even at the dawn of the 19th century, the English physicist and chemist Michael Faraday succeeded in converting chlorine and carbon dioxide into a liquid state by compressing them at very low temperatures. However, some of the gases did not succumb to scientists at that time, and, as it turned out, it was not a lack of pressure, but an inability to reduce the temperature to the required minimum.

Liquid, unlike gas, occupies a certain volume, but it also takes the form of a filled vessel below the surface. Visually, the liquid can be represented as round beads or cereals in a jar. The molecules of a liquid are in close interaction with each other, but freely move relative to each other.

If a drop of water remains on the surface, after a while it will disappear. But we remember that thanks to the law of conservation of mass-energy, nothing disappears and does not disappear without a trace. The liquid will evaporate, i.e. will change its state of aggregation to gaseous.

Evaporation - is the process of transformation of the state of aggregation of a substance, in which molecules, whose kinetic energy exceeds the potential energy of intermolecular interaction, rise from the surface of a liquid or solid.

Evaporation from the surface of solids is called sublimation or sublimation. Most in a simple way observe sublimation is the use of naphthalene to control moths. If you smell a liquid or a solid, then evaporation is occurring. After all, the nose captures the fragrant molecules of the substance.

Liquids surround a person everywhere. The properties of liquids are also familiar to everyone - this is viscosity, fluidity. When it comes to the shape of a liquid, many people say that a liquid has no definite shape. But this only happens on Earth. Due to the force of gravity, a drop of water is deformed.

However, many have seen astronauts catching water balloons of various sizes in zero gravity. In the absence of gravity, the liquid takes the form of a ball. And the force of surface tension provides the liquid with a spherical shape. Bubble- a great way to get acquainted with the force of surface tension on Earth.

Another property of a liquid is viscosity. Viscosity depends on pressure, chemical composition and temperature. Most liquids obey Newton's law of viscosity, discovered in the 19th century. However, there are a number of highly viscous liquids that, under certain conditions, begin to behave like solids and do not obey Newton's law of viscosity. Such solutions are called non-Newtonian fluids. The simplest example of a non-Newtonian fluid is a suspension of starch in water. If you act on a non-Newtonian fluid with mechanical forces, the fluid will begin to take on the properties of solids and behave like a solid.

Solid state

If, in a liquid, unlike a gas, the molecules no longer move randomly, but around certain centers, then in the solid state of matter atoms and molecules have a clear structure and look like lined up soldiers on parade. And thanks to the crystal lattice, solids occupy a certain volume and have a constant shape.

Under certain conditions, substances that are in the state of aggregation of a liquid can turn into a solid, and solids, on the contrary, when heated, melt and turn into a liquid.

This is because when heated, the internal energy increases, respectively, the molecules begin to move faster, and when the melting temperature is reached, the crystal lattice begins to break down and the aggregate state of the substance changes. For most crystalline bodies, the volume increases during melting, but there are exceptions, for example, ice, cast iron.

Depending on the type of particles that form the crystal lattice of a solid, the following structure is distinguished:

molecular

metal.

For some substances change in aggregate states occurs easily, as, for example, with water, other substances require special conditions (pressure, temperature). But in modern physics, scientists distinguish one more independent state of matter - plasma.

Plasma - ionized gas with the same density of both positive and negative charges. In wildlife, plasma is found in the sun, or during a lightning flash. The northern lights and even the familiar bonfire, which warms us with its warmth during a foray into nature, also refers to plasma.

Artificially created plasma adds brightness to any city. Neon advertising lights are just low-temperature plasma in glass tubes. Conventional fluorescent lamps are also filled with plasma.

Plasma is divided into low-temperature - with an ionization degree of about 1% and a temperature of up to 100 thousand degrees, and high-temperature - ionization of about 100% and a temperature of 100 million degrees (this is the state in which plasma in stars is).

Low-temperature plasma in fluorescent lamps familiar to us is widely used in everyday life.

High-temperature plasma is used in fusion reactions and scientists do not lose hope of using it as a replacement. atomic energy, however, the control in these reactions is very difficult. And an uncontrolled thermonuclear reaction proved to be a weapon of colossal power when, on August 12, 1953, the USSR tested a thermonuclear bomb.

Buy

To check the assimilation of the material, we offer a small test.

1. What does not apply to states of aggregation:

liquid

light +

2. The viscosity of Newtonian fluids is subject to:

Boyle-Mariotte law

the law of Archimedes

Newton's law of viscosity +

3. Why the Earth's atmosphere does not fly away into outer space:

because gas molecules cannot develop the second cosmic velocity

because the gravity of the earth acts on the gas molecules +

both answers are correct

4. What does not apply to amorphous substances:

• sealing wax

• iron +

5. When cooling, the volume increases at:

• ice +

In order to understand what the aggregate state of matter is, remember or imagine yourself in the summer near the river with ice cream in your hands. Great picture, right?

So, in this idyll, in addition to enjoyment, one can also carry out physical observation. Pay attention to the water. In the river it is liquid, in the composition of ice cream in the form of ice it is solid, and in the sky in the form of clouds it is gaseous. That is, it is simultaneously in three different states. In physics, this is called the aggregate state of matter. There are three states of aggregation - solid, liquid and gaseous.

Change in the state of aggregation of matter

We can observe the change in the aggregate states of matter with our own eyes in nature. Water from the surface of water bodies evaporates and clouds form. So the liquid turns into a gas. In winter, the water in the reservoirs freezes, turning into a solid state, and in the spring it melts again, turning back into a liquid. What happens to the molecules of a substance when it changes from one state to another? Are they changing? Are, for example, ice molecules different from vapor molecules? The answer is unequivocal: no. The molecules remain exactly the same. Their kinetic energy changes, and, accordingly, the properties of the substance. The energy of the vapor molecules is large enough to scatter in different directions, and when cooled, the vapor condenses into a liquid, and the molecules still have enough energy for almost free movement, but not enough to break away from the attraction of other molecules and fly away. With further cooling, the water freezes, becoming a solid body, and the energy of the molecules is no longer enough even for free movement inside the body. They oscillate about one place, held by the attractive forces of other molecules.

The nature of the movement and state of molecules in various aggregate states of matter can be reflected in the following table:

processes in which there is a change in the aggregate states of substances, only six.

The transition of a substance from a solid to a liquid state is called melting, reverse process - crystallization. When a substance changes from a liquid to a gas, it is called vaporization, from gas to liquid - condensation. The transition from a solid state directly to a gas, bypassing the liquid state, is called sublimation, reverse process - desublimation.

• 1. Melting
• 2. Crystallization
• 3. Vaporization
• 4. Condensation
• 5. Sublimation
• 6. Desublimation

Examples of all these transitions we have seen it many times in our lives. Ice melts to form water, water evaporates to form steam. In the opposite direction, the steam, condensing, passes back into water, and the water, freezing, becomes ice. And if you think that you do not know the processes of sublimation and desublimation, then do not rush to conclusions. The smell of any solid body is nothing but sublimation. Some of the molecules escape from the body, forming a gas that we can smell. And an example of the reverse process is the patterns on the glass in winter, when the vapor in the air, freezing, settles on the glass and forms bizarre patterns.

The aggregate state of a substance is determined by the forces acting between the molecules, the distance between the particles and the nature of their movement.

AT solid particles occupy a certain position relative to each other. It has low compressibility, mechanical strength, since the molecules do not have freedom of movement, but only vibrations. Molecules, atoms, or ions that form a solid are called structural units. Solids are divided into amorphous and crystalline(Table 27 ).

Table 33

Comparative characteristics of amorphous and crystalline substances

Crystalline substances melt at a strictly defined temperature (T pl), amorphous ones do not have a pronounced melting point; when heated, they soften (characterized by a softening interval) and pass into a liquid or viscous state. The internal structure of amorphous substances is characterized by a random arrangement of molecules . The crystalline state of matter implies the correct arrangement in space of the particles that make up the crystal, and the formation crystalline (spatial)gratings. The main feature of crystalline bodies is their anisotropy - unevenness of properties (thermal and electrical conductivity, mechanical strength, dissolution rate, etc.) in different directions, while amorphous bodies isotropic .

Solidcrystals- three-dimensional formations characterized by strict repeatability of the same structural element (elementary cell) in all directions. elementary cell- represents the smallest volume of a crystal in the form of a parallelepiped, repeated in the crystal an infinite number of times.

Basic parameters of the crystal lattice:

The energy of the crystal lattice (E cr. , kJ/mol) – this is the energy that is released during the formation of 1 mol of a crystal from microparticles (atoms, molecules, ions) that are in a gaseous state and are separated from each other by a distance that excludes their interaction.

Crystal lattice constant ( d , [ A 0 ]) – the smallest distance between the center of two particles in a crystal connected by a chemical bond.

Coordination number (c.h.) - the number of particles surrounding the central particle in space, connected with it by a chemical bond.

The points where the crystal particles are located are called lattice nodes

Despite the variety of forms of crystals, they can be classified. Systematization of crystal forms was introduced A.V. Gadolin(1867), it is based on the features of their symmetry. In accordance with the geometric shape of crystals, the following systems (syngonies) are possible: cubic, tetragonal, orthorhombic, monoclinic, triclinic, hexagonal, and rhombohedral (Fig. 18).

The same substance can have different crystalline forms, which differ in internal structure, and hence the physical and chemical properties. Such a phenomenon is called polymorphism . isomorphism – two substances of different nature form crystals of the same structure. Such substances can replace each other in the crystal lattice, forming mixed crystals.

Rice. 18. Basic systems of crystals.

Depending on the type of particles located at the nodes of the crystal lattice and the type of bonds between them, crystals are of four types: ionic, atomic, molecular and metallic(rice . 19).

Rice. 19. Types of crystals

Characteristics of crystal lattices are presented in table. 34.

Introduction

1. Aggregate state of matter - gas

2. Aggregate state of matter - liquid

3. Aggregate state of matter - solid

4. The fourth state of matter is plasma

Conclusion

List of used literature

Introduction

As you know, many substances in nature can be in three states: solid, liquid and gaseous.

The interaction of particles of matter in the solid state is most pronounced. The distance between molecules is approximately equal to their own sizes. This leads to a sufficiently strong interaction, which practically deprives the particles of the opportunity to move: they oscillate around a certain equilibrium position. They retain their shape and volume.

The properties of liquids are also explained by their structure. Particles of matter in liquids interact less intensively than in solids, and therefore they can change their location in leaps and bounds - liquids do not retain their shape - they are fluid.

A gas is a collection of molecules moving randomly in all directions independently of each other. Gases do not have their own shape, they occupy the entire volume provided to them and are easily compressed.

There is another state of matter - plasma.

The purpose of this work is to consider the existing aggregate states of matter, to identify all their advantages and disadvantages.

To do this, it is necessary to perform and consider the following aggregate states:

2. fluids

3. solids

3. Aggregate state of matter - solid

Solid, one of the four states of aggregation of matter, which differs from other states of aggregation (liquids, gases, plasmas) the stability of the form and the nature of the thermal motion of atoms that make small vibrations around the equilibrium positions. Along with the crystalline state of T. t., there is an amorphous state, including the glassy state. Crystals are characterized by long-range order in the arrangement of atoms. There is no long-range order in amorphous bodies.

In everyday practice, one has to deal not separately with individual atoms, molecules and ions, but with real substances - an aggregate a large number particles. Depending on the nature of their interaction, four types of aggregate state are distinguished: solid, liquid, gaseous and plasma. A substance can transform from one state of aggregation to another as a result of a corresponding phase transition.

The presence of a substance in a particular state of aggregation is due to the forces acting between the particles, the distance between them and the features of their movement. Each state of aggregation is characterized by a set of certain properties.

Properties of substances depending on the state of aggregation:

In accordance with the degree of order in the system, each state of aggregation is characterized by its own ratio between the kinetic and potential energies of the particles. In solids, the potential predominates over the kinetic, since the particles occupy certain positions and only oscillate around them. For gases, there is an inverse relationship between potential and kinetic energies, as a consequence of the fact that gas molecules always move randomly, and there are almost no cohesive forces between them, so the gas occupies the entire volume. In the case of liquids, the kinetic and potential energies of the particles are approximately the same, a non-rigid bond acts between the particles, therefore fluidity and a constant volume are inherent in liquids.

When the particles of a substance form a regular geometric structure, and the energy of bonds between them is greater than the energy of thermal vibrations, which prevents the destruction of the existing structure, it means that the substance is in a solid state. But starting from a certain temperature, the energy of thermal vibrations exceeds the energy of bonds between particles. In this case, the particles, although they remain in contact, move relative to each other. As a result, the geometric structure is broken and the substance passes into a liquid state. If the thermal fluctuations increase so much that the connection between the particles is practically lost, the substance acquires a gaseous state. In an "ideal" gas, particles move freely in all directions.

When the temperature rises, the substance passes from an ordered state (solid) to a disordered state (gaseous); the liquid state is intermediate in terms of the ordering of particles.

The fourth state of aggregation is called plasma - a gas consisting of a mixture of neutral and ionized particles and electrons. Plasma is formed at ultrahigh temperatures (10 5 -10 7 0 C) due to the significant collision energy of particles that have the maximum disorder of motion. A mandatory feature of plasma, as well as other states of matter, is its electrical neutrality. But as a result of the disordered motion of particles in the plasma, separate charged microzones can appear, due to which it becomes a source of electromagnetic radiation. In the plasma state, there is matter on, stars, other space objects, as well as in thermonuclear processes.

Each state of aggregation is determined, first of all, by the range of temperatures and pressures, therefore, for a visual quantitative characteristic, a phase diagram of a substance is used, which shows the dependence of the state of aggregation on pressure and temperature.

Diagram of the state of matter with phase transition curves: 1 - melting-crystallization, 2 - boiling-condensation, 3 - sublimation-desublimation

The state diagram consists of three main areas, which correspond to the crystalline, liquid and gaseous states. Individual regions are separated by curves reflecting phase transitions:

1. solid to liquid and vice versa, liquid to solid (melting-crystallization curve - dotted green graph)
2. liquid to gaseous and reverse conversion of gas to liquid (boiling-condensation curve - blue graph)
3. solid to gaseous and gaseous to solid (sublimation-desublimation curve - red graph).

The coordinates of the intersection of these curves are called the triple point, at which, under conditions of a certain pressure P \u003d P in and a certain temperature T \u003d T in, a substance can coexist in three states of aggregation at once, and the liquid and solid states have the same vapor pressure. The coordinates Pv and Tv are the only values ​​of pressure and temperature at which all three phases can coexist simultaneously.

The point K on the phase diagram of the state corresponds to the temperature Tk - the so-called critical temperature, at which the kinetic energy of the particles exceeds the energy of their interaction and therefore the line of separation between the liquid and gas phases is erased, and the substance exists in the gaseous state at any pressure.

It follows from the analysis of the phase diagram that at a high pressure greater than at the triple point (P c), the heating of a solid ends with its melting, for example, at P 1, melting occurs at the point d. A further increase in temperature from T d to T e leads to the boiling of the substance at a given pressure P 1 . At a pressure Р 2 less than the pressure at the triple point Р в, heating the substance leads to its transition directly from the crystalline to the gaseous state (point q), that is, to sublimation. For most substances, the pressure at the triple point is lower than the saturation vapor pressure (P in

P saturated steam, therefore, when the crystals of such substances are heated, they do not melt, but evaporate, that is, they undergo sublimation. For example, iodine crystals or "dry ice" (solid CO 2) behave this way.

gaseous state

Under normal conditions (273 K, 101325 Pa), both simple substances, the molecules of which consist of one (He, Ne, Ar) or several simple atoms (H 2, N 2, O 2), and complex substances with a low molar mass (CH 4, HCl, C 2 H 6).

Since the kinetic energy of gas particles exceeds their potential energy, the molecules in the gaseous state are constantly moving randomly. Due to the large distances between the particles, the forces of intermolecular interaction in gases are so small that they are not enough to attract particles to each other and keep them together. It is for this reason that gases do not have their own shape and are characterized by low density and high ability to compress and expand. Therefore, the gas constantly presses on the walls of the vessel in which it is located, equally in all directions.

To study the relationship between the most important gas parameters (pressure P, temperature T, amount of substance n, molar mass M, mass m), the simplest model of the gaseous state of matter is used - ideal gas, which is based on the following assumptions:

• the interaction between gas particles can be neglected;
• the particles themselves are material points that do not have their own size.

The most general equation describing the ideal gas model is considered to be the equations Mendeleev-Clapeyron for one mole of a substance:

However, the behavior of a real gas differs, as a rule, from the ideal one. This is explained, firstly, by the fact that between the molecules of a real gas there are still insignificant forces of mutual attraction that compress the gas to a certain extent. With this in mind, the total gas pressure increases by the value a/v2, which takes into account the additional internal pressure due to the mutual attraction of molecules. As a result, the total gas pressure is expressed by the sum P+ a/v2. Secondly, the molecules of a real gas have, albeit a small, but quite definite volume b , so the actual volume of all gas in space is V- b . When substituting the considered values ​​into the Mendeleev-Clapeyron equation, we obtain the equation of state of a real gas, which is called van der Waals equation:

where a and b are empirical coefficients that are determined in practice for each real gas. It is established that the coefficient a has a large value for gases that are easily liquefied (for example, CO 2, NH 3), and the coefficient b - on the contrary, the higher in size, the larger the gas molecules (for example, gaseous hydrocarbons).

The van der Waals equation describes the behavior of a real gas much more accurately than the Mendeleev-Clapeyron equation, which, nevertheless, is widely used in practical calculations due to its clear physical meaning. Although the ideal state of a gas is a limiting, imaginary case, the simplicity of the laws that correspond to it, the possibility of their application to describe the properties of many gases at low pressures and high temperatures, makes the ideal gas model very convenient.

Liquid state of matter

The liquid state of any particular substance is thermodynamically stable in a certain range of temperatures and pressures characteristic of the nature (composition) of the substance. The upper temperature limit of the liquid state is the boiling point above which a substance under conditions of stable pressure is in a gaseous state. The lower limit of the stable state of the existence of a liquid is the temperature of crystallization (solidification). Boiling and crystallization temperatures measured at a pressure of 101.3 kPa are called normal.

For ordinary liquids, isotropy is inherent - the uniformity of physical properties in all directions within the substance. Sometimes other terms are also used for isotropy: invariance, symmetry with respect to the choice of direction.

In the formation of views on the nature of the liquid state, the concept of the critical state, which was discovered by Mendeleev (1860), is of great importance:

A critical state is an equilibrium state in which the separation limit between a liquid and its vapor disappears, since the liquid and its saturated vapor acquire the same physical properties.

In the critical state, the values ​​of both densities and specific volumes of the liquid and its saturated vapor become the same.

The liquid state of matter is intermediate between gaseous and solid. Some properties bring the liquid state closer to the solid. If solid substances are characterized by a rigid ordering of particles, which extends over a distance of hundreds of thousands of interatomic or intermolecular radii, then in the liquid state, as a rule, no more than a few tens of ordered particles are observed. This is explained by the fact that orderliness between particles in different places of a liquid substance quickly arises, and is just as quickly “blurred” again by thermal vibrations of particles. At the same time, the overall density of the “packing” of particles differs little from that of a solid, so the density of liquids does not differ much from the density of most solids. In addition, the ability of liquids to compress is almost as small as in solids (about 20,000 times less than that of gases).

Structural analysis confirmed that the so-called short range order, which means that the number of nearest "neighbors" of each molecule and their mutual arrangement are approximately the same throughout the volume.

A relatively small number of particles of different composition, connected by forces of intermolecular interaction, is called cluster . If all particles in a liquid are the same, then such a cluster is called associate . It is in clusters and associates that short-range order is observed.

The degree of order in various liquids depends on temperature. At low temperatures slightly above the melting point, the degree of order in the placement of particles is very high. As the temperature rises, it decreases and, as the temperature rises, the properties of the liquid approach the properties of gases more and more, and when the critical temperature is reached, the difference between the liquid and gaseous states disappears.

The proximity of the liquid state to the solid state is confirmed by the values ​​of the standard enthalpies of vaporization DH 0 of evaporation and melting DH 0 of melting. Recall that the value of DH 0 evaporation shows the amount of heat that is needed to convert 1 mole of liquid into vapor at 101.3 kPa; the same amount of heat is spent on the condensation of 1 mole of vapor into a liquid under the same conditions (i.e. DH 0 evaporation = DH 0 condensation). The amount of heat required to convert 1 mole of a solid to a liquid at 101.3 kPa is called standard enthalpy of fusion; the same amount of heat is released during the crystallization of 1 mole of liquid under normal pressure conditions (DH 0 melting = DH 0 crystallization). It is known that DH 0 evaporation<< DН 0 плавления, поскольку переход из твердого состояния в жидкое сопровождается меньшим нарушением межмолекулярного притяжения, чем переход из жидкого в газообразное состояние.

However, other important properties of liquids are more like those of gases. So, like gases, liquids can flow - this property is called fluidity . They can resist the flow, that is, they are inherent viscosity . These properties are influenced by attractive forces between molecules, the molecular weight of the liquid substance, and other factors. The viscosity of liquids is about 100 times greater than that of gases. Just like gases, liquids can diffuse, but at a much slower rate because liquid particles are packed more densely than gas particles.

One of the most interesting properties of the liquid state, which is not characteristic of either gases or solids, is surface tension .

A molecule located in a liquid volume is uniformly acted upon by intermolecular forces from all sides. However, on the surface of the liquid, the balance of these forces is disturbed, as a result of which the surface molecules are under the action of some resultant force, which is directed inside the liquid. For this reason, the liquid surface is in a state of tension. Surface tension is the minimum force that keeps the particles of a liquid inside and thereby prevents the surface of the liquid from contracting.

Structure and properties of solids

Most of the known substances, both natural and artificial, are in the solid state under normal conditions. Of all the compounds known today, about 95% are solids, which have become important, since they are the basis of not only structural, but also functional materials.

• Structural materials are solids or their compositions that are used to make tools, household items, and various other structures.
• Functional materials are solids, the use of which is due to the presence of certain useful properties in them.

For example, steel, aluminum, concrete, ceramics belong to structural materials, and semiconductors, phosphors belong to functional ones.

In the solid state, the distances between the particles of matter are small and have the same order of magnitude as the particles themselves. The interaction energies between them are large enough, which prevents the free movement of particles - they can only oscillate about certain equilibrium positions, for example, around the nodes of the crystal lattice. The inability of particles to move freely leads to one of the most characteristic features of solids - the presence of their own shape and volume. The ability to compress solids is very small, and the density is high and little dependent on temperature changes. All processes occurring in solid matter occur slowly. The laws of stoichiometry for solids have a different and, as a rule, broader meaning than for gaseous and liquid substances.

The detailed description of solids is too voluminous for this material and is therefore covered in separate articles:, and.